Sash balance



-D. TAPPAN SASH BALANCE April 14, 1942'.

Filed March 30.1 1940 I I u INVENTOR flew 77- 7;;PPA/V A TO Patented Apr. 14, 1942 SASH BALANCE Dewitt Tappan, Rochester, N. Y., assignor to The Caldwell Manufacturing 00., Rochester, N. Y., a corporation of New York Application March 30, 1940, Serial No. 326,983

7 Claims.

This invention relates to sash balances and particularly to balances utilizing a tension spring in combination with block and tackle means for balancing the sash in the window frame. In order to make such a spring balance practical so that the sash will be balanced by its tension in any and all positions in the frame, it is essential that the active tension exerted by the spring is equalized during the expansion and contraction of the spring by the operation of the block and tackle. Only in this way can the sash be moved to any desired position in the window frame Without either rising or dropping from such position on the release thereof. A spring without propercontrolling means provides a very inefiicient balancing effect on a sash. If it is adjusted to balance the sash in. its lowered position in the window frame, that is at the end of the expansion of the spring, it cannot balance the sash and hold it in its raised position at the beginning of the expansion of the spring when practically no tension is exerted by the spring to hold the sash in its raised position. On the other hand an adjustment of the spring to provide sufiicient tension for holding the sash in its raised position will cause such an increased tension of the spring in the lowering of the sash that the weight of the sash is quickly overbalanced by the increased tension and causes the sash to partially move back toward its raised position on the release thereof.

To overcome this defect in spring balances of this type my present invention has for its principal object to provide a simple but efiicient controllingmeans for the movement of the block and tackle which equalizes the active tension of the balancing spring so that it will balance the weight of the sash in any of its. positions in the window frame.

A further object of this invention is to provide means whereby the tension of the spring may. be increased or decreased to permit the balance of windows of varying weights.

Another object of this invention is to provide .a-sash balance which can be readily mounted in the sash of a window and quickly and easily connected to the window frame.

A still further object of this invention is to provide a sash balance which is adapted to be attached to the sash as a unitary structure for movement therewith.

All these and other objects and attendant advantages of this invention will become more readily apparent fromrthe description of one embodiment of the invention, reference being had to the accompanying drawing in which Figure 1 is a front elevation of a. portion of a Window frame and sash with the sash balance incorporated in the sash and a portion of the sash illustrated in section. I

Figure 2 is a vertical sectional view taken on the line 2-2 of Figure 1. v

Figure 3 is a detail sectional. View of a portion of the window frame. taken on the line 33. of Figure 1 so. as to illustrate the attachment of the strap of the sash balance to, the window frame.

Figure 4 is a horizontal sectional view taken meral I indicates the upper right hand portion of a window frame withv a portion of a'window sash 2 adapted to move up and down in the window frame. The edge of the sash is grooved C to receive the sash balance which is incorporated in the channel shaped frame or mounting member 3. The upper end of this: mounting channel is reduced in width toreceivethe standing block 4 of a. block and tackle and have the. shafts 5 and 6 of its pulleys" 1- and 8 extend thru the sides of the channel and headed over on the outside thereof for the attachment of the standing block to the mounting channel. The standing block is provided with an extension 9. and on top of this extension is provided the bifurcated bracket l0 which is used inthe connection of the sash balance to the window frame as will hereinafter appear. A suitable'hole' in the extension 9 permits an anchoring screw l I to fasten the upper portion of the mounting channel into the groove; of; the sash. I

At the bottom the mounting channel 3 has attached thereto the angle bracket 12 anda flange l3 forming anextension of this'bracket is provided with a hole for use with the anchoring screw I4 in the attachment of the lower end of the mounting channel into the groove of the sash. i

Cooperating with the standing block 4 is the running block I5 which, is movable in the mounting channel and comprises a substantially rectangular frame in which. the: pulleys. l6 and 11.;

are mounted to rotate" The expansion spring I8 is anchored at the bottom of the mounting channel and for this purpose is provided at the bottom with a plug l9. This plug is threaded to receive the combined anchoring and adjustment screw 20 which passes thru the angle bracket l2 so as to have its head 2| located on the outside thereof. In this way adjustment of the tension of the spring is readily made at the bottom of the mounting channel by means of a suitable screw driver as will hereinafter be described.

The upper end of the expansion spring I 8 is attached to the bottom of the running block I5 and a strap 22 in the form of a metal ribbon is attached to the running block and winds around the pulleys of both the standing block and the running block so that the free end of the strap is adapted to be anchored to the anchoring hook 23 on the window frame by means of its anchoring loop 24. It has been found in practice that the metal tape used for the strap 22 operated most eificiently when its thickness is substantially t or less of the radii of the pulleys in the standing and running blocks over which the strap passes in its operation of the block and tackle.

As illustrated in Figure l the strap is attached to the running block at 25 and extends up over the pulley 8 of the standing block, then down under the pulley I6 of the running block, then up over the pulley 1 of the standing block and again down under the pulley ll of the running block and finally up to the anchoring hook 23 where the strap is anchored to the window frame as above pointed out. The metal ribbon thus travels from the running block to the standing block and back to the running block in overlapping planes with the pulleys of both the running and the standing block so that the connecting loops of the ribbon between the blocks are in constant frictional contact with each other and produce a braking action on the movement of the ribbon. This braking action may be increased by having one or all of the pulleys held stationary in the blocks so that the ribbon instead of riding over the pulleys will have to frictionally slide over them. Further braking action may be produced by having the ribbon slide over each consecutive pair of pulleys with a plurality of loops, as for example by having the ribbon travel in overlapping planes from the running block to the standing block and back again to connect the first two pulleys twice as illustrated in Figure 6 before the ribbon passes onto the next two pulleys of the blocks. It will be apparent that while the contacting areas of the strap are reduced as the running block moves toward the standing block, their frictional contact is increased by the increasing tension of the balancing spring on the expansion thereof. This compensates for the reduction in the contacting areas of the strap and keeps the active tension of the balancing spring substantially uniform for the purpose of balancing the weight of the sash many of its positions within the frame. The attachment of the strap at 25 is to a portion of the top of the frame l5 of the running block from which it passes thru a slot 25A to the under side of the top of this frame and thence to the pulley 8 of the standing block 4 as above described. In this Way the strap is firmly held on running block with operative expansion of the spring I8 is limited thereby. For this reason the number of turns of the strap over the pulleys between the standing and running blocks are adapted to provide the predetermined limited movement of the running block and consequent expansion of the spring so that the full range of movement of the sash will cause a movement of the running block and an expansion and contraction of the spring within the length of the balance. To make this practical and at the same time make possible the use of a spring of maximum length, the spring used in my balance is provided with an initial tension. In winding or forming this spring the coils thereof are forced together so tightly that a predetermined force is required to separate them for the expansion of the spring. Where a normally wound spring would have to be expanded from ten to fifteen per cent of its length before it will exert sufficient force to balance the sash in its elevated or starting position my spring will thus have an initial tension without expansion to perform this same function.- This makes possible the use of a longer spring with a correspondingly longer expansion and contraction without distortion thereof and reduces the length of adjustment of the spring necessary for balancing the sash. The movement of the block and tackle during the expansion and contraction of the spring is absolutely silent so that a sash equipped with this type of balance will be perfectly silent in its movement in the window frame.

The connection of the sash balance with the window frame is extremely simple and requires no skill so that it may be accomplished by any one. After the mounting channel is fastened into the groove of the sash the strap 22 is tensioned until the anchoring loop 24 thereof has where the top of the loop 24 is slightly above and opposite to the top of the anchoring hook 23 on the window frame. In this position the upper end of the loop 24 is swung over the anchoring hook 23 so that when the sash is lowered the hook automatically engages the loop 24 and forces loop 24 01? the bracket [0 leaving the window sash suspended by the strap 22. When it is desired to remove the sash from the window frame, the anchoring loop 24 can be readily forced out of engagement with the anchoring hook 23 onto the bracket l0 in substantially the same easy manner.

Of course the sash balance shown and described may be changed in various ways, and variations may be required under certain conditions, therefore, While the constructional details are deemed preferable and I have shown and described them specifically, it is to be understood that I do not limit myself to such precise construction, but consider that I am at liberty to make such changes and alterations as fairly said spring being anchored to said mounting member and said strap passing from said running block over the pulley of each of the blocks in overlapping planes with the pulleys and portions of the strap in frictional contact with each other to frictionally control the movement of said running block during the expansion and contraction of said tension spring by means of said strap.

2. In a sash balance the combination as set forth in claim 1 in which said strap extends between the block in a plurality of superimposed frictionally contacting loops.

3. In a sash balance the combination of a mounting member, a standing block on said mounting member, a plurality of pulley members carried by said standing block spacedly mounted one above the other, a running block movable intermediate the mounting member, a plurality of pulley members spacedly carried by said running block one above the other, a strap attached to one end of said running block, a tension spring attached to the other end of said running block, said tension spring being anchored to said mounting member and said strap passing from said running block over the pulley members of both of said blocks in overlapping planes with the pulley members to provide for the movement of said running block toward and away from said standing block by means of said strap with portions of said strap in constant frictional contact with each other to frictionally control the movement of said running block during the expansion and contraction of said spring by means of said strap.

4. In a sash balance the combination as set forth in claim 3 in which said strap passes consecutively between one of the pulleys of the standing block and one of the pulleys of the running block with a plurality of superimposed frictionally contacting loops.

5. In a spring sash balance for mounting in a groove of a sash, the combination of a channel member, anchoring means at the top and bottom of said channel member for attachment into said groove, a spring anchored to one end of said channel member, a standing block in the other .end of said channel member, a pulley carried by said standing block, a running block movable in said channel attached to said spring, a pulley carried by said running block, and a strap connecting said blocks and movable over said pulleys in overlapping planes with said pulleys and with portions of the strap in frictional contact with each other.

6. In a spring balance the combination of a mounting member, a standing block attached to one end of said mounting member and a tension spring attached to the other end of said mounting spring, a running block attached to said spring, a strap connecting said running block with said standing block in overlapping planes with the pulleys of said blocks and with sections of said strap between said blocks in frictional contact so as to equalize the increasing and decreasing tension of said spring on said strap by the decreasing and increasing frictional contact of the strap sections in the movement of the running block by said strap toward and away rom said standing block.

'7. In a spring sash balance using a spring tensioned strap for its connection with a fixed anchoring member on the window frame, the combination of an anchoring bracket carried by said sash to one side of the normal plane of movement of said strap, an anchoring loop carried by said spring tensioned strap and removably held tensioned on the bracket for swinging movement into and out of engagement with said fixed anchoring member and bodily movement away from said anchoring bracket into the normal plane of movement of said strap.

DEWITT TAPPAN. 

